Imported to library pictures has unique names.

Excluded case of trying to determine mime type for empty string.

Added items has icons.

Now oriented to Top.

Added UUIDs for each imported item.
Supported groups.

Groups reads fine for strokes.

Import ubz works bad with groups.

Implemented import UBZ strokes from CFF (means strokes who was exported from UBZ to CFF and imported back).
Compatible with groups.